A Moloney murine sarcoma virus (MSV) specific P60 polyprotein consisting of p30, p15 and p12 is detected in all cells transformed by the ml isolate of MSV. The observed properties of P60 in transformed cells may provide insight into the question of how virus transformation antigens are metabolized. BIBLIOGRAPHIC REFERENCES: Robey, W.G., Graham, B.J, Harris, C.L., Madden, M.J., Pearson, G.F. and Vande Woude, G.F.: Persistent herpes simplex virus infections established in two Burkitt lymphoma derived cell lines. J. Gen. Virol. 32: 51-62, 1976. Robey, W.G., Oskarsson, M.K., Vande Woude, G.F., Naso, R.B., Arlinghaus, R.B., Haapala, D.K. and Fischinger, P.J.: Cells transformed by certain strains of Moloney sarcoma virus contain murine P60. Cell 10: 79-89, 1977.